1. Field of the Invention
The present invention relates to a composition for being sprayed on the foliage of a plant, in which a semiconductor photocatalyst is included as an essential component; and a use of the same.
2. Detailed Description of the Prior Art
The decrease of carbon dioxide assimilation (e.i., photosynthesis) in a field crop directly means that a harvesting is decreased. Conventionally, in an agricultural land, in order to have a good harvest, a massive commitment of fertilizers, a carbon dioxide treatment and the like have been carried out, and thereby some effects have been provided; however, when an amount of sunshine was insufficient due to an environmental factor such as weather, on the contrary, such treatments sometimes affected harvests.
Furthermore, in order to control an excess luxuriant growth of the foliage of a plant, an auxin based hormone agent, a gibberellin biosynthesis inhibitor, an ethylene producing agent and the like are sometimes used; however, it is the present states of things that a lot of them are apt to cause a chemical injury to a plant, and provide even a human body with a high toxicity.
Besides, as a countermeasure against diseases causing great damage to field crops, novel bactericides which took years before development have been brought to market practically every year; however, even when any novel bactericide is used, a drug-resistant bacteria occurs in several short years, thus effects often come not to be provided as expected. Therefore, it has been hurried to develop a method of controlling diseases, which is quite different in function therefrom.
In particular, in recent years, an agricultural chemicals residue and/or a dioxin in field crops constitutes a social problem; however, as a method of removing these toxic or deleterious substances before a consumer practically eats a crop, there is no effective manner except washing, which is in a problem.
On the other hand, basic research on photodecomposition of water wherein a semiconductor photocatalyst is used has been carried out from a long time; in recent years, a tile in which titanium oxide is used (refer to Japanese Patent Laid-Open Publication No.209985/94), an apparatus for purifying water (refer to Japanese Patent Laid-Open Publication No.47687/96), and the like are put to practical use. The property that when a semiconductor photocatalyst has received light energy larger than band-gap energy, an electrically positive valence band and an electrically negative conduction band are formed in the crystal is applied to these. When a water system in which a semiconductor photocatalyst is included is exposed to light irradiation, an oxidation reaction of water [4H2O(4H++4OHxe2x88x92)] as shown by the following formula {circle around (1)} is advanced near the valence band, while a reduction reaction of a material as shown by the following formula {circle around (2)} is advanced near the conduction band.
xe2x80x834OHxe2x88x92xe2x86x92O2+2H2O,xe2x80x83xe2x80x83the formula {circle around (1)}
4H+xe2x86x922H2.xe2x80x83xe2x80x83the formula {circle around (2)}
Furthermore, near the valence band, in a process wherein the above-mentioned reaction is advanced, hydroxyl group is oxidized into hydroxy radical (.OH), while near the conduction band, oxygen is subjected to one electron reduction, and thereby superoxide anion radical (O2xe2x88x92) is formed.
Besides, when carbon dioxide or carbonate ion exists in these systems, near the conduction band, a reduction reaction of CO2 as shown in the following formula {circle around (3)} is advanced:
CO2+nH+xe2x86x92CO, HCHO, CH3OH, CH4.xe2x80x83xe2x80x83the formula {circle around (3)}
The reaction through which this CO2 is reduced is a reaction as referred to as xe2x80x9can artificial photosynthesisxe2x80x9d, which is studied in many research institutions. However, these research examples merely relate to researches at a basic research level, which are to the backbone concentrated on the sides of phenomena such as a partial analysis of the mechanism of photosynthesis, and a mere photodecomposition of water. Furthermore, a lot of the research examples have the problems that (1) the activity of a catalyst is very low and is not efficient; (2) a method of preparing a catalyst, or the conditions of reaction are complicated; (3) a reverse reaction is large; and the like. Thus, it is the present state of things that the above research examples are far from being put to practical use.
In an agricultural land, in order to have a good harvest, a massive commitment of a fertilizer, a herbicide, a bactericide, an insecticide and the like have been carried out, and thereby some effects have been provided; however, even at the present time when technologies have been developed, it is a serious problem for persons being engaged in agriculture how to prevent a crop as driven into an underdeveloped state when an amount of sunshine has been insufficient. Furthermore, in the midst of time when the disruption of the living organisms environment due to a chlorine compound is cried, it is of urgent necessity to develop a growth regulator and/or a method of controlling disease, which are environmental and safe.
It is a first object of the present invention to provide a composition for being sprayed on the foliage of a plant so as to solve conventional problems, wherein the composition is suspended in water so as to apply to the foliage of the plant by using a paint sprayer or the like, so that the photodecomposition of water on the surface of the foliage is advanced, and thereby carbon dioxide assimilation in the plant can be expedited, and an oxygen free radical as produced in a process of a photodecomposition reaction of water can be used for a lipid peroxidation reaction in a plant cell membrane, and the generation of ethylene, which is one of plant hormones, is expedited, and consequently, the plant growth such as the dwarf of the plant, the promotion of rooting in a capillary root thereof, the promotion of date of maturity, the formation of an abscission layer, or the induction of flower bud can be controlled, and furthermore, Phyto-alexin, which is derived by a lipid peroxidation reaction is accumulated, and thereby a disease resistance for the plant can be provided, and a bactericide, an insecticide, a growth regulator and/or a herbicide which are excessively left on the surface of the foliage can be decomposed; and it is a second object of the present invention to provide a method of using such a composition for being sprayed on the foliage of the plant.
The inventors concerned have earnestly and repeatedly studied thereabout, and consequently, it has been found that the above-mentioned problems can be solved, wherein a composition comprising a semiconductor photocatalyst providing little load to environment, as an essential ingredient, and if necessary, further comprising a carbonate and/or a hydrogencarbonate, wherein the photocatalyst can be easily prepared, and the condition of reaction is simple, is sprayed on a plant, and thereby, the photodecomposition of water on the surface of foliage can be expedited, and photosynthesis can be supplemented when an amount of sunshine was insufficient, while the growth of the plant can be controlled. Thus, the present invention has been made.
The invention claimed in claim 1 relates to a composition for being sprayed on the foliage of a plant, characterized in that said composition comprises at least one semiconductor photocatalyst(s) as an active ingredient, or if necessary, further comprises at least one carbonate(s) and/or hydrogencarbonate(s).
The invention claimed in claim 2 relates to a composition for being sprayed on the foliage of a plant according to claim 1, characterized in that the composition is used as a photosynthesis accelerator which accelerates water decomposition so as to accelerate a photosynthesis in the plant.
The invention claimed in claim 3 relates to a composition for being sprayed on the foliage of a plant according to claim 1, characterized in that the composition is used as a plant growth regulator which accelerates a lipid peroxidation reaction so as to derive ethylene, which is one of plant hormones, and thereby controls the growth of the plant.
The invention claimed in claim 4 relates to a composition for being sprayed on the foliage of a plant according to claim 1, characterized in that the composition is used as a disease-resistance providing agent which accelerates a lipid peroxidation reaction so as to derive Phyto-alexin in a plant, and thereby provides a disease resistance for the plant.
The invention claimed in claim 5 relates to a composition for being sprayed on the foliage of a plant according to claim 1, characterized in that the composition is used as a decomposing agent which accelerates water decomposition so as to produce an oxygen free radical, and thereby decomposes a bactericide, an insecticide, a growth regulator and/or a herbicide which are excessively left on the surface of the foliage.
The invention claimed in claim 6 relates to a composition for being sprayed on the foliage of a plant according to claim 1, characterized in that the composition is used as a chemical agent which has two or more effects selected from the group consisting of a photosynthesis accelerator, a plant growth regulator, a disease-resistance providing agent and a decomposing agent.
The invention claimed in claim 7 relates to a composition for being sprayed on the foliage of a plant according to any one of claims 1 to 6, characterized in that the semiconductor photocatalyst(s) is included in an amount of 0.0005 percent to 50 percent by weight of the total weight of the composition.
The invention claimed in claim 8 relates to a composition for being sprayed on the foliage of a plant according to any one of claims 1 to 7, characterized in that a weight ratio of the semiconductor photocatalyst(s) to the carbonate(s) and/or hydrogencarbonate(s) is selected from the range of 1:20000 to 1:1.
The invention claimed in claim 9 relates to a composition for being sprayed on the foliage of a plant according to any one of claims 1 to 8, characterized in that the semiconductor photocatalyst(s) is titanium oxide.
The invention claimed in claim 10 relates to a composition for being sprayed on the foliage of a plant according to claim 9, characterized in that the titanium oxide is of anatase-type.
The invention claimed in claim 11 relates to a composition for being sprayed on the foliage of a plant according to claim 9 or 10, characterized in that the average particle size of the titanium oxide is in the range of 1 nm to 500 nm.
The invention claimed in claim 12 relates to a composition for being sprayed on the foliage of a plant according to any one of claims 1 to 11, characterized in that the carbonate(s) and/or the hydrogencarbonate(s) is water soluble.
The invention claimed in claim 13 relates to a composition for being sprayed on the foliage of a plant according to claim 12, characterized in that the carbonate(s) and/or hydrogencarbonate(s) is selected from the group consisting of Na2CO3, NaHCO3, K2CO3 and KHCO3.
The invention claimed in claim 14 relates to a use of a composition for being sprayed on the foliage of a plant according to any one of claims 1 to 13, characterized in that the composition is sprayed on the above-ground part of the plant.
The invention claimed in claim 15 relates to a use of a composition for being sprayed on the foliage of a plant according to claim 14, characterized in that the composition is applied to the plant by diluting with water wherein the upper limit of dilution is 100,000 times.
The invention claimed in claim 16 relates to a use of a composition for being sprayed on the foliage of a plant according to claim 14 or 15, characterized in that the composition is mixed with one or more adjuvant(s) selected from the group consisting of a nonionic, anionic, cationic or amphoteric surface active agent, a fixing agent, a thickener, a suspending agent, a neutralizer, an antiseptic agent and a dust diluent so as to be applied to said plant.
The invention claimed in claim 17 relates to a use of a composition for being sprayed on the foliage of a plant according to any one of claims 14 to 16, characterized in that the composition is mixed with at least one Hill oxidant so as to be applied to said plant.